Not just fertilizer...

By Elsa Youngsteadt

Students at the University of Montana have been scooping bison poop in Yellowstone National Park not to tidy up the prairie but to discover evolutionary and ecological relationships between the bison herds in the park.

They found that they can extract bison DNA from the feces; if, that is, they get it when it's fresh. This gives them the material they need to study herd genetics without traumatizing the animals themselves. The DNA in question comes from the bison's mitochondria, cellular organelles involved in respiration, and inherited only through the maternal lineage. Because of its rapid rate of evolution and simple pattern of inheritance, mitochondrial DNA is ideal for studies of evolutionary relationships within a species.

Based on the mitochondrial DNA sequences, the researchers found that there are at least two distinct breeding populations of bison in the park, each of which harbors different forms of the mitochondrial genes. The work suggests new conservation and management approaches to the Yellowstone bison, which were previously believed to be a single homogeneous population.

The study also highlights evolution in action. This is not to say that the Yellowstone bison are on the verge of forming different species, but simply that distinct groups of the animals have, in fact, undergone different changes in gene frequencies over time. This kind of evolutionary change is referred to as microevolution to distinguish it from macroevolution, or evolutionary change at or above the species level.